1. Field of the Invention
The invention is related to the field of magnetic head lifting devices in a tape recorder in which the drive source for the lifting device is the turning force of a capstan shaft.
2. Description of the Prior Art
In prior art tape head lifting devices a magnetic head is maintained in resilient contact with a stepped cam surface of a disklike cam and the cam is rotated by an electromagnet. This rotation of the cam causes a change in the portion of the stepped cam surface which is in contact with the head and thereby causes the magnetic head to move up and down. In this prior device, however, a bulky electromagnet is required to rotate the cam and this results in the device becoming very large. In addition, a large amount of electric power is consumed which results in a serious disadvantage for portable tape player/recorders which are battery powered.
To overcome the above-mentioned deficiencies, a tape recorder was developed in which the drive source for moving the magnetic head is the turning force of a capstan shaft. One such recorder is disclosed in U.S. Pat. No. 3,877,071 assigned to the same assignee as the present invention. In this type of recorder, a ring is fastened to a capstan shaft and serves as a means to utilize the turning force of the capstan shaft to lift the magnetic head. The ring is normally opposite an indented portion formed in a peripheral edge of a rotary body. The rotary body is initially rotated by the driving force of an electromagnet so that the ring will subsequently engage the nonindented peripheral edge of the body. The rotary body is then rotated by the ring until the ring is again opposite an indented portion of the rotary body, which therefore results in disengaging the rotary body from the ring. This prior head lifter device tends to malfunction in that the rotary body is often excessively rotated because of its inertia, and this results in the rotation of the rotary body beyond its desired stop position which in turn results in a reengagement between the ring and the nonindented portions of the peripheral edge of the rotary body. Therefore when such a head lifting device is used to switch between different tape tracks in a multi-track tape player, the excessive rotation can result in a nondesired skipping of one or more tape tracks.